netmap & chelsio

[np at FreeBSD.org]

On Fri, Jul 06, 2018 at 06:41:53AM +0000, Eggert, Lars wrote:
> Hi,
> 
> On 2018-7-5, at 17:47, np at FreeBSD.org wrote:
> > Set hw.cxgbe.fl_pktshift=0 in loader.conf to stop the chip from doing
> > this.  See cxgbe(4) for details on the knob.  It's a historic
> > optimization that doesn't seem to matter on modern CPUs, so the driver
> > default should probably be 0 instead of 2.
> 
> thanks, I must have missed this in the man page.
> 
> Looking at this in detail now, I wonder if there are other loader
> settings that should be set for netmap use, such as
> hw.cxgbe.buffer_packing=0 and/or hw.cxgbe.allow_mbufs_in_cluster=0?

The driver uses dedicated tx/rx queues for netmap and those queues use
netmap provided buffers instead of driver allocated mbuf+cluster used by
normal rx queues.  buffer_packing and allow_mbufs_in_cluster are not
applicable to netmap queues.

Regards,
Navdeep